How to escape from Tsunami?

Ways to prevent from Tsunami Disaster

- If you are at school, please follow the instructions of school head and teachers.
- If you are at home, let all family members know the warning information of Tsunami. If you are living in a Tsunami hazardous zone, make preparation for the prevention or move your dwelling from the hazardous zone to the safety places.
- If you are on the coast or nearby regions of the ocean at the time of earthquake occurrence (or if you feel the ground shaking), move immediately to the higher places.
- When you are on coast and feel the ground shaking, please do not wait until the warning information has come, move immediately to the higher places. Like moving away from the coast and ocean, please also move far away from the places nearby the rivers and streams which are connected with the sea and ocean.
- If the epicenter of the earthquake is far, the time to escape from the tsunami is enough. If it is near, the time is too short to move to the higher elevation places (hill or small mountain) because thetsunami could be reached within a few minutes.
- Chain of islands, coasts with the shallow depth and mangrove forests can make the tsunami wave disintegrate and weaken. But very strong and high tsunami wave can damage such situation. Living far from coastal flat land is the most safety way to escape from the tsunami disaster.
- The higher floor of several-stories-reinforced building (like hotels) at the coastal low land is one of the safe places to escape from the tsunami wave. But please avoid small houses and buildings which are not well structured and built for the resistance of the tsunami wave.

Reasons for the weakness of tsunami along the coast of Myanmar
- North-south trending earthquake belt starts at the south of Cocos island, continues until the northern part of Yakhine state. But no earthquake occurrence was recorded in the northern part of earthquake belt, the inland part of northern Yakhine state, and this portion is stated as the seismic gap.
- Therefore great earthquakes seldom occur in the Myanmar territorial water.
- Due to the presence of this seismic gap, even large earthquake could happen but its depth will be greater than 70 km (Such earthquake could not induce tsunami generation.).

Physical and technical characteristics of tsunami wave
How fast does tsunami wave travel?

Date
26 December 2004

Region
Sumatra Island

Direction

East-west
South-north

Speed of wave

800-1000 km/hr
400-500 km/hr


Arrival time of tsunami wave after the earthquake event

- West coast of Sumatra island 10 Minutes
- Phuket, Thailand 1 Hour
- Sri Lanka 2 Hours
- India 2 Hours
- Myanmar 3 Hours
- Kenya and Somalia 7 Hours

How does tsunami wave travel?

There are two assumptions for the motion of tsunami wave.
The first assumption is that generally tsunami wave travels in two directions. The first direction leads to the nearest coast from the tsunami source and the second one to the opposite direction that is commonly regarded as the open sea.
The second assumption is that tsunami wave travels towards two directions perpendicular to the long earthquake rupture.
The largest and powerful waves of 2004 Sumatra tsunami traveled mainly east-west direction perpendicular to the 1200 km long north-south trending Myanmar-India earthquake rupture.

How does Tsunami occur?

Causes for occurance of Tsunami

As a tsunami leaves the deep water of the open ocean and travels into the shallower water near the coast, it transforms. A tsunami travels at a speed that is related to the water depth - hence, as the water depth decreases, the tsunami slows. The tsunami's energy flux, which is dependent on both its wave speed and wave height, remains nearly constant. Consequently, as the tsunami's speed diminishes as it travels into shallower water, its height grows. Because of this shoaling effect, a tsunami, imperceptible at sea, may grow to be several meters or more in height near the coast. When it finally reaches the coast, a tsunami may appear as a rapidly rising or falling tide, a series of breaking waves, or even a bore.

As a tsunami approaches shore, it begins to slow and grow in height. Just like other water waves, tsunamis begin to lose energy as they rush onshore - part of the wave energy is reflected offshore, while the shoreward-propagating wave energy is dissipated through bottom friction and turbulence. Despite these losses, tsunamis still reach the coast with tremendous amounts of energy. Tsunamis have great erosional potential, stripping beaches of sand that may have taken years to accumulate and undermining trees and other coastal vegetation. Capable of inundating, or flooding, hundreds of meters inland past the typical high-water level, the fast-moving water associated with the inundating tsunami can crush homes and other coastal structures. Tsunamis may reach a maximum vertical height onshore above sea level, often called a runup height, of 10, 20, and even 30 meters.

Tsunamis are formed as a result of earthquakes, volcanic eruptions, or landslides that occur under the sea. When these events occur under the water, huge amounts of energy are released as a result of quick upward bottom movement. For example, if a volcanic eruption occurs, the ocean floor may very quickly move upward several hundred feet. When this happens, huge volumes of ocean water are pushed upward and a wave is formed. A large earthquake can lift thousands of square kilometers of sea floor which will cause the formation of huge waves. The Pacific Ocean is especially prone to tsunamis as a result of the large amount of undersea geological activity.
In the open ocean tsunamis may appear very small with a height of less than 1 meter (3 feet). Tsunamis will sometimes go undetected until they approach shallow waters along a coast. These waves have a very large wavelength (up to several hundred miles) that is a function of the depth of the water where they were formed. Although these waves have a small height, there is a tremendous amount of energy associated with them. As a result of this huge amount of energy, these waves can become gigantic as they approach shallow water. Their height, as they crash upon the shore, depends on the underwater surface features. They can be as high as 30 m (100 feet) or more. In 1737 , a huge wave estimated to be 64m (210 feet) in height hit Cape Lopatka, Kamchatka (NE Russia). The largest Tsunami ever recorded occurred in July of 1958 in Lituya Bay, Alaska. A huge rock and ice fall sent water surging up to a high water mark of 500m (1640 feet). It's no wonder that these waves can cause such massive destruction and loss of life.

n order for a tsunami caused by a seaquakes to occur, three things have to be happen:
1: The Earthquake must measure at least 7,0 on the Richter scale. Only from this intensity upwards is there enough energy released to rapidly displace enough water to create the tsunami.
2: The sea bed must be lifted or lowered by the earthquake. If the sea bed is displaced sidewards, no tsunami will occur as, for example, happened during the earthquake of 28 March, 2005 off the western coast of Sumatra.
3: The epicentre of the earthquake must be near to the earth's surface.

The difference between tsunamis and normal waves or waves caused by strong wind is the extreme distances between wavelengths. This is the distance from one wave crest to the next wave crest, which can be between 100 and 300 km. A further feature of tsunamis is their relatively small wave height on the open sea - mostly between half a metre and one meter. Even though they can travel up to 1 000 km/h, these waves are generally not noticeable in deep waters. The wave itself only becomes dangerous once it reaches land. In coastal areas where water levels gradually become shallower, the wave will slow down but tower into a wave wall as much as 30 meters high. The reason for this is the mass of water and energy contained in the tsunami wave. Whereas only the upper water layers are being moved in wind created waves, with a Tsunami wave, an entire mass of water from the sea bed to the surface is in motion.

If a trough of a tsunami wave approaches the land first, the water will be pulled back into the sea by enormous currents. Vast stretches of the seabed are often drained as happened during the December 2004 tsunami. In this case, and if recognised, people on the beach and beachfronts have between a few minutes and half an hour to escape to higher ground. The time to escape depends on when the wave crest strikes.

The first wave, that can grow to be up to 30 meters high at the beach, will usually be followed by more waves that are sometimes even more dangerous. Not only the crests of waves are dangerous but also the troughs, since their currents can pull people and whole houses many miles into the sea.

The Tsunami Alarm warning time can be between a few minutes up to several hours, depending on distance from the earthquake's epicentre.

What is Tsunami?

Tsunami disaster

What is Tsunami?

Tsunami is a Japanese word with the English translation, "harbor wave." The phenomenon we call tsunami is a series of large waves of extremely long wavelength and period usually generated by a violent, impulsive undersea disturbance or activity near the coast or in the ocean. When a sudden displacement of a large volume of water occurs, or if the sea floor is suddenly raised or dropped by an earthquake, big tsunami waves can be formed by forces of gravity. Earthquakes, landslides, volcanic eruptions, explosions, and even the impact of cosmic bodies, such as meteorites, can generate tsunamis. Tsunamis can savagely attack coastlines, causing devastating property damage and loss of life.

How do earthquakes generate tsunamis?

Tsunamis can be generated when the sea floor abruptly deforms and vertically displaces the overlying water. Tectonic earthquakes are a particular kind of earthquakes that are associated with the earth's crustal deformation; when these earthquakes occur beneath the sea, the water above the deformed area is displaced from its equilibrium position. Waves are formed as the displaced water mass, which acts under the influence of gravity, attempts to regain its equilibrium. When large areas of the sea floor elevate or subside, a tsunami can be created.

What happens when a tsunami encounters land?

Just like other water waves, tsunamis begin to lose energy as they rush onshore - part of the wave energy is reflected offshore, while the shoreward-propagating wave energy is dissipated through bottom friction and turbulence. Despite these losses, tsunamis still reach the coast with tremendous amounts of energy. Tsunamis have great erosional potential, stripping beaches of sand that may have taken years to accumulate and undermining trees and other coastal vegetation. Capable of inundating, or flooding, hundreds of meters inland past the typical high-water level, the fast-moving water associated with the inundating tsunami can crush homes and other coastal structures. Tsunamis may reach a maximum vertical height onshore above sea level, often called a run up height, of 10, 20, and even 30 meters.

Speed of tsunami

Tsunami wave can travel at the speed of a commercial jet plane, over 800 km/h. They can move from one side of the Pacific Ocean in less than a day. The waves can be extremely dangerous and damaging when they reach the shore.

What should you do?

1. If you are at home and hear there is a tsunami warning, you should make sure your entire family is aware of the tsunami. Your family should evacuate your house if you live in a tsunami evacuation zone.

2. If you are at the beach or near the ocean and you feel the earth shake, move immediately to higher ground. Do not wait for a tsunami warning to be announced.

3. If you are on a ship or boat, do not return to port if you are at sea and a tsunami warning has been issued for your area. Tsunami can cause rapid changes in water level and unpredictable dangerous current in harbours and ports.

The phenomenon we call "tsunami" (soo-NAH-mee) is a series of traveling ocean waves of extremely long length generated by disturbances associated primarily with earthquakes occurring below or near the ocean floor. Underwater volcanic eruptions and landslides can also generate tsunamis. In the deep ocean, their length from wave crest to wave crest may be a hundred miles or more but with a wave height of only a few feet or less. They cannot be felt aboard ships nor can they be seen from the air in the open ocean. In deep water, the waves may reach speeds exceeding 500 miles per hour.

Tsunamis are a threat to life and property to anyone living near the ocean. For example, in 1992 and 1993 over 2,000 people were killed by tsunamis occurring in Nicaragua, Indonesia and Japan. Property damage was nearly one billion dollars. The 1960 Chile Earthquake generated a Pacific-wide tsunami that caused widespread death and destruction in Chile, Hawaii, Japan and other areas in the Pacific. Large tsunamis have been known to rise over 100 feet, while tsunamis 10 to 20 feet high can be very destructive and cause many deaths and injuries.

The Tsunami Warning System (TWS) in the Pacific, comprised of 26 participating international Member States, monitors seismological and tidal stations throughout the Pacific Basin. The System evaluates potentially tsunamigenic earthquakes and disseminates tsunami warning information. The Pacific Tsunami Warning Center (PTWC) is the operational center of the Pacific TWS. Located in Honolulu, Hawaii, PTWC provides tsunami warning information to national authorities in the Pacific Basin.

How do tsunami differ from other water waves?
Tsunamis are unlike the wind-generated waves on local lakes or coastal beaches, in that they are characterized as shallow-water waves, with long periods and wavelengths. The wind-generated swell like the one at a California beach spawned by a storm out in the pacific and rhythmically rolling in, one wave after another might have a period of about 10 seconds and a wavelength of 150 m. A tsunami, on the other hand, can have a wavelength in excess of 100 km and period on the order of one hour. As a result of their long wave lengths tsunami behave as shallow-water waves. A wave becomes a shallow water wave when the ratio between the water depth and its wave length gets very small. Shallow-water waves move at a speed that is equal to the square root of the product of the acceleration of gravity (9.8 m/s/s) and the water depth. This means, in the Pacific Ocean, where the typical water depth is about 4000m, a tsunami travels at about 200m/s, or over 700 700km/hr. Because the rate at which a wave losses its energy is inversely related to its wavelength, tsunami not only propagate at high speeds, they can also travel great, transoceanic distances with limited energy losses. The wave crests bend as the tsunami travels—is called refraction. Wave refraction is caused by segments of the wave moving at different speeds as the water depth along the crest varies.

How does earthquake generate tsunami?
Tsunami can be generated when the see floor abruptly deforms and vertically displaces the overlying water. Tectonic earthquakes are a particular kind of earthquake that are associated with the earth’s crustal deformation, when these earthquakes occur beneath the see, the water above the deformed area is displayed from its equilibrium position. Waves are formed as the displaced water mass, which acts under the influence of gravity, attempts to regain its equilibrium.


Tsunami safety Rules:
An earthquake in an area is a natural tsunami warning. Do not stay in low-lying coastal areas after a strong earthquake has been felt.

A tsunami is not a single wave, but a series of waves. Stay out of danger areas until competent authority issues an “all-clear”.

All tsunamis like hurricanes are potentially dangerous; even though they may not damage every coastline they strike.

Never go down to the shore to watch for a tsunami. When see the wave you are too close to escape it. Never try to surf a tsunami; tsunamis do not curl or break like surfing waves.

Sooner or later, tsunamis visit every coastline in the Pacific. Warnings apply to you if you live in any Pacific coastal area.

Tsunami warning Organization

ITIC:
The International Tsunami Information Center (ITIC) was established in Honolulu, in November 1965, by the Intergovernmental Oceanographic Commission (IOC) of the United Nations Educational, Scientific and Cultural Organization (UNESCO).
In 1968, IOC formed an International Coordination Group for the Tsunami Warning System in the Pacific (ICG/ITSU).

The present Member States are:
Australia, Canada, Chile, China, Colombia, Cook Islands, Costa Rica, Democratic People’s Republic of Korea, Ecuador, El Salvador, Fiji, France, Guatemala, Indonesia, Japan, Mexico, New Zealand, Nicaragua, Peru, Republic of the Philippines, Republic of Korea, Russian Federation, Samoa, Singapore, Thailand, and the United States of America.

The International Tsunami Warning System in the Pacific is one of the most successful international scientific programs with the direct humanitarian aim of mitigating the effects of tsunami by saving lives and property.

Damages: Loss or harm caused by a destructive tsunami. More specifically, the damage caused directly by tsunamis can be summarized into the following: 1) deaths and injuries; 2) houses destroyed, partly destroyed, inundated, flooded, or burned; 3) other property damage and loss; 4) boats washed away, damaged or destroyed; 5) lumber washed away.